For-profit wikifarm, founded by Jimmy Wales.
Wikia, formerly Wikicities, is a for-profit organization which hosts over one hundred thousand wikis. That's a hell of a lot of poorly written, copyleft crapola. The site hosts, and has hosted, quite a number of well-known wikis, including Uncyclopedia and WikiFur (before WikiFur decided to self host).
Founded in 2004 by Jimmy Wales and Angela Beesley as a for-profit counterpart to Wikipedia, Wikia was first founded under the name of Wikicities and remained as such for about two years before assuming its current name because, people being people, first-time users were perplexed to find that the site was essentially 'a city of wikis', rather than 'a wiki of cities'.
In 2007 Wikia played a role in the explosive Essjay drama, which starred a salaried Wikia employee being called out for lying about his credentials and in reality being a 24 year old community college dropout rather than the highly qualified individual he was purported to be. As events unfolded and the web of lies he had spun began to unravel Jimmy Wales requested that Essjay quit his positions within both Wikimedia and Wikia and the unfolding drama was reported on by the New York Times. Wales even issued a public apology and tried to establish a knee-jerk system by which people's credentials could be verified, but this was shot down.
During April of 2010, Wikia announced the creation of its 100,000th wiki.
Still quite popular — 100,000 wikis don't lie.